Python map() Function

numbers = [2, 4, 6, 8, 10]

# returns the square of a number
def square(number):
  return number * number

# apply square() to each item of the numbers list
squared_numbers = map(square, numbers)

# converting to list for printing
result = list(squared_numbers)
print(result) # Output: [4, 16, 36, 64, 100]

map() Syntax

Its syntax is:

map(function, iterables)

map() Arguments

The map() function takes two arguments:

• function - a function that is applied to each element of the iterables
• iterables - iterables such as lists, tuples, etc

Note: We can pass more than one iterable to the map() function.

map() Return Value

The map() function returns a map object, which can be easily converted to lists, tuples, etc.

Example 1: Working of map()

def square(n):
    return n*n

numbers = (1, 2, 3, 4)
result = map(square, numbers)
print(result)

# converting the map object to set
result = set(result)
print(result)

Output

<map object at 0x7f722da129e8>
{16, 1, 4, 9}

In the above example, each item of the tuple is squared and then converted to a set.

Example 2: map() with Lambda

In a map() function, we can also use a lambda function instead of a regular function. For example,

numbers = (1, 2, 3, 4)
result = map(lambda x: x*x, numbers)
print(result)

# convert to set and print it
print(set(result))

Output

<map 0x7fafc21ccb00>
{16, 1, 4, 9}

There is no difference in functionalities of this example and Example 1.

Example 3: map()

In this example, we have passed two iterables to the map() function.

num1 = [1, 2, 3]
num2 = [10, 20, 40]

# add corresponding items from the num1 and num2 lists
result = map(lambda n1, n2: n1+n2, num1, num2)
print(list(result))

Output

[11, 22, 43]